1. Field of the Invention
The present invention relates to a complete or partial shoulder or hip prosthesis making it possible to reproduce, with an improved degree of precision, the characteristics of a natural joint.
2. Description of the Related Art
In the domain of shoulder prostheses, it is known, for example from European Patent Application 0 299 889, to create a convex articular surface on a glenoid component, while a concave articular surface of corresponding shape is formed on a humeral component. The glenoid component of such a surface is very invasive and a subacromial conflict of the humeral component may occur at the end of a movement of abduction.
Furthermore, U.S. Pat. No. 4,846,840 discloses producing, on an intermediate element of a prosthesis, two substantially concentric convex surfaces with a view to their articulation on concave surfaces of corresponding shapes, provided respectively on two bones to be articulated on each other. Such a prosthesis is unstable, particularly due to the offset between the two sets of articular surfaces provided in this prosthesis.
It is a more particular object of the invention to overcome these drawbacks by proposing a shoulder or hip joint prosthesis reproducing the anatomical articulation, while facilitating the abduction of the arm or the leg, in the absence of the cover of the rotators for the shoulder or of the stabilizing structures of the hip, thanks to an increase of the lever arm of the effort exerted by the deltoid muscle or the gluteus medius muscle at the beginning of abduction.